Chapter 3 - 9/5/2011 WhataretheGoals(Chapter3)?

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9/5/2011 1 What are the Goals (Chapter 3)? Recognize and understand chemical equations. Learn to balance chemical equations. Recognize some basic reaction types: combination, decomposition, combustion. Understand formula weights and molecular weights. Understand Avogadro’s number and the mole. Understand how empirical formulas can be determined by experiments. Stoichiometry – quantitative information from balanced reactions. Understand limiting reactants. Chemical processes convert: Elements into compounds Compounds into elements Compounds into compounds Chemical Basics
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9/5/2011 2 Chemical Equations Chemical Reaction – Involves a rearrangement of atoms , one or more substances are transformed (reactant) and one or more substances are created (product). Conservation of Mass – Atoms are neither created nor destroyed during a chemical reaction. Balanced Chemical Equation – Tells us which substances are the products and which substances are the reactants, and the relative amounts of each. Chemical Equations These show the chemical change taking place in a reaction. Physical state Sr ( s ) + Cl 2( g ) SrCl 2( s ) Reactants Product
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9/5/2011 3 Chemical Equations As matter cannot be created or destroyed in a chemical reaction, the total number of atoms on one side must be equal to the total number of atoms on the other. Simple Patterns of Chemical Reactivity Combination: A + B C2 S(s) + 3 O 2 (g) 2 SO 3 (g) Decomposition: C A + BC a C O 3 (s) CaO(s) + CO 2 (g) Combustion in air (a.k.a. burning, oxidation) C 3 H 8 (g) + 5 O 2 (g) 4 H 2 O(g) + 3 CO 2 (g)
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9/5/2011 4 Chemical Reactions - Combustion • Combustion in Air (including combustion analysis) Combustion Reactions Rapid reactions that produce a flame Reaction of a substance with O 2 Combustion of hydrocarbons forms CO 2 and H 2 O. Example 1 - Combustion of Methane Let’s try to write a balanced equation for this reaction C H 4 + O 2 CO 2 + H 2 O (Balance H first) Now we can look to balance the numbers of oxygen atoms . CH 4 + 2 O 2 CO 2 + 2H 2 O 2
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9/5/2011 5 Chemical Reactions (Combustion) • Attempt to show on paper what is happening at the laboratory and molecular levels. Combination and Decomposition Reactions Decomposition CaCO 3 (s) CaO(s) + CO 2 (g) Combination, balanced 2Mg(s) + O 2 (g) 2MgO(s) (s) = Solid (l) = Liquid (g) = gas (aq) = A compound dissolved in water to form a solution
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9/5/2011 6 __C 2 H 4 (g) + __O 2 (g) -> __CO 2 (g) + __H 2 O(l) __Al(s) + __HCl(aq) -> __AlCl 3 (s) + __H 2 (g) __CH 4 O(l) + __O 2 (g) -> __CO 2 (g) + __H 2 O(l) BALANCING EQUATIONS 2 2 3 1 1 3 1.5 1 12 1.5 1 Chemical Equations Example Cyclohexane burns in oxygen to give carbon dioxide and water Reactants: Cyclohexane, C 6 H 12 Oxygen, O 2 Products: Carbon Dioxide, CO 2 Water, H 2 O
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9/5/2011 7 Chemical Equations Example Initially, we can write the reaction as C 6 H 12 + O 2 CO 2 +H 2 O This is NOT a correct equation – there are unequal numbers of atoms on both sides Reactants: 6 C, 12 H, 2 O Products: 1 C, 2 H, 3 O Balancing the equation 6 C, 12 H, 2 O 1 C, 2 H, 3 O 6 C on LHS means there must be 6 C on the RHS C 6 H 12 + O 2 CO 2 2 O C 6 H 12 + O 2 6CO 2 2 O
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This note was uploaded on 02/08/2012 for the course SCIENCE 1201 taught by Professor Bill during the Spring '11 term at LSU.

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Chapter 3 - 9/5/2011 WhataretheGoals(Chapter3)?

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